Why is a component's installation date more useful than its manufacture date?

Service life is consumed by use, not by sitting in a warehouse, so the clock that matters starts when a component was put into service. The gap between the two dates is usually small but occasionally large: equipment held in distribution, a unit bought and stored, or a component salvaged from another building can carry a manufacture date years before it began working. Reading remaining life from the data plate alone therefore overstates age in exactly those cases. The practical difficulty is that manufacture date is usually determinable — encoded in the serial number or printed on the plate — while installation date usually is not, so the inspector reports what is determinable, notes the basis, and treats it as an approximation. Permit records, installer stickers and the age of adjacent work are the usual corroborating evidence.

A component begins accumulating wear when it is placed in service, so installation date defines the period of actual use, which is what remaining service life depends on.

Service life is consumed by operation, so installation date determines accumulated wear. Manufacture date is usually determinable from serial numbers; installation date is inferred from installer labels, permit records or adjacent work.

The Clock Starts at Startup, not at the factory. A unit in a warehouse ages on the calendar, not on the meter.

Where a manufacture date long predates the surrounding work, say so. It usually means stored or salvaged equipment and it changes the age estimate.

• •Reading remaining life from manufacture date alone
• •Not stating which date the age estimate is based on
• •Overlooking installer stickers and permit evidence